Compressed air is roughly 78% Nitrogen, 21% Oxygen, 1% Argon and small percentages of other gases. By using a zeolite molecular sieve to separate compressed air, the primary constituent/s are removed depending on the size of the pores in the sieve. This means that if you have a pore size of 4 angstroms (*) you can only let molecules smaller than that size pass through it. This is where the separation comes into play. The oxygen molecule has a diameter of 3 angstroms allowing it to freely pass through the sieve, however, nitrogen isn't small enough to pass through it, thus being trapped inside the molecular sieve.
You can also find out more about the concentration of different gases in air by looking at the percentage breakdown.
Compressed air is roughly 78% Nitrogen, 21% Oxygen, 1% Argon and small percentages of other gases.
The molecular sieve zeolite is a key component of the oxygen-separation process. It has a complex structure that allows it to selectively remove nitrogen and other gases from compressed air, leaving behind only oxygen as the primary constituent of air.
When you compress air to high pressure, you're compressing all its molecules into a smaller space. This means they're closer together than they were before—and closer together than they'd be in natural conditions. At these high pressures, nitrogen gas can pass through pores in the molecular sieves that are too small for oxygen molecules (whose diameters are about twice as large). This is why zeolites work better at lower temperatures: when their pores are smaller overall and thus more easily plugged by nitrogen gas molecules' larger size.
Molecular sieves are made of a crystalline structure with pores that are too small for certain molecules to pass through. The size of the pores depends on the material used to make the molecular sieve and can range from 0.4 angstroms (*) to 0.8 nm (**). There's no way around this fact: if you do not have a pore size that is smaller than the molecule you want to keep out, then it will pass through.
The * symbol indicates an uncertainty in measurement and is not part of formal IUPAC notation; this symbol has been added here for clarity in case readers prefer not to use it themselves when writing about molecular sieves or discussing them with others.
In order to separate the oxygen from nitrogen, a molecular sieve must first be used. A molecular sieve is an advanced type of porous material that has been synthesized specifically with pores small enough to allow only certain molecules and atoms through while rejecting others.
The pores in this material can be very small in size, allowing them to trap molecules. They are often used as filters in medical equipment or industrial settings where they need to separate out very specific elements or molecules based on their size and shape. The molecular sieves used for this process are designed specifically for separating oxygen from nitrogen because they have larger pores than other types of molecular sieves (3 angstroms), which allows them to trap oxygen molecules while letting smaller ones pass through unimpeded. This is where the separation comes into play: The oxygen molecule has a diameter of 3 angstroms allowing it to freely pass through the sieve, however, nitrogen isn't small enough to pass through it, thus being trapped inside the molecular sieve
Zeolites are crystalline substances with a pore diameter of about 4 angstroms. Oxygen molecules are small enough to pass through the sieve, but nitrogen molecules are not.
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